Cummins/Onan — Bleeding trailer brakes
Maintenance · Trailer brake system
From a Cummins/Onan service manual covering: 4A2.3, 6A3.4-GS, 6AT3.4-GS, DL4, DL6, QSA3, QSA4, QSA6. Check it applies to your exact model before use.
Applies to: Cummins/Onan DGAB, Cummins/Onan DGAC, Cummins/Onan DGAD, Cummins/Onan DGAE, Cummins/Onan DL4, Cummins/Onan DL6
Procedure
- Fill system with DOT-3 heavy duty hydraulic fluid using pressure type brake bleeder.
- Install bleeder hose on first wheel to be bled; submerge loose end in glass container of brake fluid.
- Loosen bleeder screw one turn; bleeding is complete for wheel when bubbling stops; close screw securely.
- Repeat bleeding at other wheel, replenishing fluid so level does not fall below half in master cylinder reservoir.
- After bleeding, ensure master cylinder reservoir is filled and filler cap securely in place.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Use DOT-3 heavy duty hydraulic fluid.
Full service-parts list: Cummins/Onan DGAB →, Cummins/Onan DGAC →, Cummins/Onan DGAD →, Cummins/Onan DGAE →, Cummins/Onan DL6 →
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.